Broadcast Receiver RF Circuit With Spurious Cancellation Path
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Solution Overview
Problem
Conventional semiconductor integrated circuits for receivers face significant challenges in reducing spurious noise, which degrades reception performance due to integration of multiple functions on a single IC chip, leading to interference and sensitivity issues.
Innovation Solution
A configuration is introduced where a second RF circuit with grounded input terminal, equivalent to the output impedance of the antenna circuit, is added to detect and cancel spurious components by combining its output with the first mixer's output 180 degrees out of phase, using an amplifier-attenuator to adjust the spurious component's frequency and level for effective cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple functions (RF, IF, baseband signal processing) are integrated onto a single IC chip, then device size is reduced and integration is facilitated, but spurious noise is introduced into the RF amplifier circuit causing degradation in reception performance
Solution Approach 1:
The invention divides the RF circuit into two separate sections: a first RF circuit that processes the received signal, and a second RF circuit that is intentionally designed to receive spurious noise generated within the IC. This segmentation allows the spurious noise to be isolated and processed separately from the main signal path, enabling noise cancellation without compromising the integrated design benefits.
Solution Approach 2:
A third RF circuit is introduced as an intermediary component that receives spurious noise from the second RF circuit and generates a cancellation signal. This intermediary circuit acts as a mediator that converts the harmful spurious noise into a useful cancellation signal that can be combined with the main signal path to reduce noise interference.
2Ease of operation
If a superheterodyne architecture is used, then signal processing is enabled, but beat output from IF signal causes degradation in reception performance
Solution Approach 1:
The invention extracts the spurious noise component from the main signal path by routing it through a dedicated second RF circuit. This extracted noise is then processed separately and used to generate a cancellation signal, effectively removing the harmful beat output from the reception path while preserving the superheterodyne signal processing capabilities.
3Device complexity
If crystal oscillator and logic circuits are integrated onto the same chip, then integration degree is increased, but beat component and noise component are introduced to RF circuit causing degradation in receiver sensitivity
Solution Approach 1:
The invention implements a feedback mechanism where the second RF circuit continuously monitors spurious noise generated by integrated components (crystal oscillator, logic circuits), and the third RF circuit generates a cancellation signal based on this feedback. This feedback loop enables the system to dynamically compensate for noise introduced by high-degree integration, maintaining receiver sensitivity despite increased integration complexity.
Data Source
AI summary
A semiconductor integrated circuit for broadcast receivers, which integrates an RF circuit, a mixer, an IF circuit, and an intermediate-frequency signal processing circuit onto a single chip, additionally includes a second RF circuit whose input terminal is grounded through an impedance equivalent to or almost the same as the output impedance of an antenna circuit, and a second mixer downstream of the second RF circuit. The second RF circuit and the second mixer each has an input impedance equivalent to that of the received signal subsystem; therefore, a spurious component equivalent to the spurious component contained in the output signal of the received signal subsystem is detected in the second RF circuit and in the second mixer, and cancels out the spurious component contained in the output signal of the received signal subsystem. Accordingly, the effects of noise due to spurious can be effectively reduced.